Talk:Autonomic nervous system
I am surprised that the author of “The Lower Brainstem and Bodily Homeostasis”, which contains a paragraph entitled "”Visceral neurons, Afferent, and Efferent” not the “autonomic nervous system”", and a critique of the lasting effects of Langley’s oversight of visceral afferents, would co-sign an article presenting the ANS as “a collection of motor neurons”. Even the Kandel textbook, after many years, has finally amended its definition into “the autonomic nervous system is a visceral sensory and motor system”, I thought, in part, thanks to William Blessing’s landmark book. What is the rationale for this reversal to the more conventional and less illuminating view?
For the most part, I agree with the comment made by the reviewer who entered the comment on visceral afferents (24th September). It is only sensible to consider a control system in terms of both its motor effects, and the afferent information that it receives in order to exert its motor effects. I thus subscribe to the view that visceral afferents ought to be included in any description of the autonomic nervous system. Langley, in his 1903 introduction to the ANS, wrote that it is possible to “consider as afferent autonomic fibres those which give rise to reflexes in autonomic tissues, and which are incapable of directly giving rise to sensation”. However, at a later time he defined the autonomic as a purely efferent system, due to the difficulty of making an adequate and exclusive definition of autonomic afferent neurons (Langley, 1921). The discovery of reflex circuits that are completely contained in the wall of the intestine, and the identification of the primary afferent neurons of these reflex circuits (Kirchgessner et al., 1992, Kunze et al., 1995, Furness., 2006) has obliged investigators to reconsider the inclusion of autonomic afferents in discussions of the ANS. Included amongst visceral afferent neurons that provide information about the states of autonomically innervated organs, but whose activation does not ordinarily lead directly to any conscious sensation of the state of the organ, or to somatic movement, are tension receptors in the carotid sinus and aortic arch, arterial chemoreceptors, and mechanoreceptors that appear to occur in all hollow organs. The information conveyed by these autonomic visceral afferent neurons is utilised to direct the activity of autonomic efferent pathways, either those supplying the same organ or supplying other organs. References: Langley, J. N. 1903. The autonomic nervous system. Brain 26, 1-26: Furness, J. B. 2006. The Enteric Nervous System. Blackwell, Oxford. 278 pp
- This further comment by John Furness, October 9, 2007.
Reviewer A: One small clarification
Use of the term "motor neurons" and "final mtor neurons" for ganglionic cells may ne useful but some readers might be confused with the "true" motor nueorns, with somata within the CNS and axons that innervate somatic (skeletal) muscle. Suggest adding a disclaimer to this effect.
Reviewer B: concise and correct
Professors Gibbins and Blessing have done a great job in boiling down a big subject into a concise summary. There are omissions, but none detract from the value of the entry as it stands.
One could include more details about synaptic mechanisms, but perhaps that would be better in a separate entry. One can also argue about some of the nomenclature as pointed out by Professor Furness, but again this is probably beyond the scope of a encyclopedic article.
I agree that it is very important to correct deep-seated misconceptions concerning the all or none nature of sympathetic and parasympathetic antagonism. The more useful principle in my view is to think of these divisions as functional antagonists working together. It is also important to reinforce the concept that the autonomic nervous system is essential for a normal life. When it breaks the patient is ill.
As for higher and lower forms of function it becomes an interesting philosophical problem. We use the power of our reason and intellect to write inspired prose and poetry. We write about feelings and autonomic behaviors- love, battle, eating, etc.
Another great example of integration is the concept of feeding. One can not eat or eliminate without the somatic motor system. Digestion depends upon the autonomic motor system. Both must work together for normal life.
Exercise also illustrates the point. To run and play a sport one must coordinate the somatic and autonomic motor systems.
Sympathectomy experiments in the 1950's helped foist the misconception that the autonomic system is not essential. Look back, in this same era, prefrontal lobotomies were promoted as an acceptable medical therapy for mental illness. Both concepts were flawed and should be rejected.